| 摘要 |
A video detection unit is provided with a first control loop including a phase detector for comparing phases between the output of a voltage-controlled oscillator and the carrier of a VIF signal to output a control voltage, and a second control loop including a counter for measuring the output frequency of the oscillator to output a control voltage when the frequency is out of a predetermined range. The second control loop determines the free-run frequency of the oscillator. The first control loop makes the frequency and phase of the oscillator coincide with those of a carrier. The output of the counter is also used as an AFT voltage.
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